Stilbene 03 08 2015 What distribution of the two products do you get Depends on Bromine ion Two possible cations that can form o The alkene attacks bromine you get a cyclic brominum atom Bromine is super big it sits across both carbons forming a cyclic cation and a Br two dots Next only way Br can attack is if goes underneath of the triangle and attacks one of the C s You get the same product no matter what carbon it attacks Distribution 100 Produces meso stilbene o Second you can get an acyclic cation Bromine on one carbon plus on the other and Br two dots Next it can attack either from the bottom or the top No restriction like the cyclic one On top dl On the bottom meso Distribution 50 50 Actual reaction Mostly meso o Neither 100 nor 50 50 so what happened Can t both cations exist at the same time They are in equilibrium Equilibrium favors the cyclic cation Talk about keck clamp change o In order to release pressure and not have any bromine fly out o Only interested in meso compound so we remove dl via of the top recrystallization Problematic solvent is xylene Volume large volume 50 mL Boiling point of xylene 140 C So time boil it 30 45 minutes let it cool down Will take an hour to an hour and a half 03 08 2015 03 08 2015
View Full Document
Unlocking...